Procedure For Manufacture Of A Tube For Conveyance Of A Fluid Of A Heat Exchanger, And Tube Obtained By Such Procedure

ABSTRACT

The present invention concerns a procedure for manufacture of a tube for conveyance of a fluid of a heat exchanger, such tube being of the type presenting a substantially rectangular cross-section, formed by two opposed walls of greater width and two rounded walls of lesser width, said procedure consists of realising the following stages: a) Commencing from a metal sheet ( 2 ), realisation of a plurality of corrugations ( 3 ) by employing an embossing process; b) Realisation of the bending of sheet ( 2 ) by employing a process of embossing or forming; and c) Proceeding to weld the free edges ( 4 ) to close tube, considering the tolerances required.

The present invention relates to a procedure for manufacture of a tube for conveyance of a fluid of a heat exchanger. The invention also relates to the tube obtained by such procedure.

The invention is particularly applicable in exchangers having recirculation of exhaust gases from an engine (EGRC).

BACKGROUND OF THE INVENTION

In some heat exchangers for cooling gases, for example those employed in systems of recirculation of exhaust gases towards the admission of an explosion engine (systems denominated “Exhaust Gas Recirculation” or EGR), the gases circulate through a bank of parallel tubes housed within a casing, during such circulation being cooled by heat exchange with a cooling fluid circulated within the housing, externally to the tubes for the passage of the gases.

Tubes for gas of rectangular section are known suitable for fitting in an optimised manner within the housing of an exchanger of rectangular section. Such tubes of rectangular section are manufactured from a circular tube and may also present corrugations having the objective of improving thermal performance of the heat exchanger. Generally such corrugations extend along the length of the tube, however without reaching the radius of the tube, i.e. the unformed circular ends thereof.

Currently the sole known method to enable the machining of the corrugations along the length of the tube in its totality is by a hydroforming process.

The procedure for manufacture of this type of tube is as follows:

Initially, the starting material is a smooth tube of circular section obtained commencing from a bent and welded sheet. Subsequently, the tube is subjected to a hydroforming process including two stages: firstly forming of the tube is proceeded to it going from having a circular section to a substantially rectangular section, and subsequently the corrugations are realised. Finally, cutting off the ends of the tube and deburring is realised, if required.

Nevertheless this procedure for manufacture of such a tube presents the following disadvantages:

-   -   The cost of the procedure for manufacture is high due to the         combination of diverse processes. On the one hand, the bent and         welded tube employed as raw material already possesses added         value; on the other hand, the hydroforming process operates at         slow cycle rates, it not being a continuous process; it         additionally requires high investment given that the machinery         and tools are of considerable expense.     -   The level of waste from the procedure for manufacture is high         because during the hydroforming process it is necessary to have         a zone of circular section at the ends of the tube wherein the         cylinders of the hydroforming machine will be positioned to seal         and inject the liquid under high pressure. As a result such         zones of circular section must be eliminated to obtain the final         shape of the tube.

DESCRIPTION ON THE PRESENT INVENTION

The objective of the procedure for manufacture of a tube for conveyance of a fluid of a heat exchanger of the present invention is to overcome the disadvantages presented by the procedures known in the art, providing a procedure for manufacture of the tubes having a lower cost.

The procedure for manufacture of a tube for conveyance of a fluid of a heat exchanger subject of the present invention, such tube being of the type presenting a substantially rectangular cross-section formed by two opposed walls of greater width and two rounded walls of lessor width, is characterised in that it consists of the realisation of the following stages:

-   -   a) Commencing from a metal sheet, realisation of a plurality of         corrugations employing an embossing process;     -   b) Realisation of bending of the sheet employing a process of         embossing or forming; and     -   c) Proceeding to weld the free edges to close the tube,         considering the tolerances required.

In this manner a procedure for manufacture is achieved entailing the combination in one production line of three different technologies: corrugation embossing, bending and welding.

Optionally, following stage c), cutting off the extreme ends of the tube is proceeded to, if required.

The principal advantages obtained through the procedure of the present invention are:

-   -   Reduction in costs of production because the process is         continuous and, consequently, cycle rates achieved are higher         than those achieved employing the process of hydroforming the         tube.     -   Reduction in waste material because employing this procedure it         is unnecessary to dispose of a greater quantity of material,         solely 1 mm on each side being sufficient for execution of the         welding points, not as occurred in the case of hydroforming         wherein at least 14 mm was required.     -   Higher production capacity achieved.     -   Lower level of investment because the machinery and tools are         more inexpensive than those employed for the tube realised by         hydroforming.     -   Less industrial plant space is required.

Preferably, the corrugations are embossed in those zones of the metal sheet corresponding to the opposed walls of greater width of the tube once fabricated, attaining part of the rounded walls of lesser width.

According to one embodiment of the present invention, the corrugations are defined by a plurality of mutually parallel linear grooves transversely crossing said walls of greater width in a direction substantially diagonal to the axis of the tube.

Advantageously, such corrugations are embossed along the metal sheet, attaining the extreme ends or avoiding the extreme ends.

Preferably, such corrugations are distributed in a manner being mutually non-equidistant, and non-symmetrical with respect to the bend line, having the objective of improving the loss of load.

In such case the corrugations are distributed maintaining the same angle of inclination such that once the metal sheet has been bent, corrugations of one wall are positioned in a crossed manner with reference to those of the opposed wall, each pair of associated corrugations defining a projection substantially in the form of an X.

Preferably, the metal sheet is bent in half in accordance with a longitudinal central line.

According to another aspect the invention also relates to a tube for conveyance of a fluid of a heat exchanger of the type obtained employing the procedure for manufacture previously defined.

BRIEF DESCRIPTION OF THE DRAWINGS

Having the objective of facilitating the description of that previously stated, some drawings are attached wherein, schematically and solely as a non-limitative example, there is represented a practical case of embodiment of the procedure for manufacture of a tube for conveyance of a fluid of a heat exchanger of the present invention, wherein:

FIG. 1 shows a metal sheet as starting material;

FIG. 2 shows the metal sheet having corrugations executed in accordance with stage a) of the procedure;

FIG. 3 shows the process of bending the sheet in accordance with stage b) of the procedure; and

FIG. 4 shows the finished tube once stages c) and d) have been realised.

DESCRIPTION OF A PREFERRED EMBODIMENT

The procedure for manufacture of a tube 1 for conveyance of a fluid of a heat exchanger according to the present invention consists of the following stages:

Initially, the starting material is a metal sheet 2 of approximately 60 mm (see FIG. 1).

Then, realisation of a plurality of corrugations 3 is proceeded to employing an embossing process along the metal sheet 2, avoiding attaining the longitudinal central zone 6 (see FIG. 2). Such corrugations 3 may be embossed along the metal sheet 2 in its entire length, or avoiding the extreme ends 5.

Subsequently, realisation of bending of sheet 2 in half is proceeded to in accordance with a longitudinal central line, employing a process of embossing or forming. In FIG. 3 are shown different phases of bending of sheet 2 in order to enable closure of tube 1.

Finally, welding free edges 4 to close tube 1 is proceeded to considering the tolerances required and, if necessary, cutting off extreme ends 5 of tube 1 to achieve the tolerances (see FIG. 4).

Although in the attached figures a pattern of corrugations in the form of parallel lines orientated in a diagonal direction may be observed, it is possible to apply any other type of pattern appropriate for the characteristics of the exchanger and type of fluid to be cooled.

The procedure of the present invention provides a reduction in costs of manufacture because, on the one hand, it is unnecessary to realise the prior operation of forming the sheet into a round tube, as occurred in the procedures known in the state of the art and, on the other hand, a totally continuous procedure is achieved. 

1. A procedure for manufacture of a tube (1) for conveyance of a fluid of a heat exchanger, such tube (1) being of the type presenting a substantially rectangular cross-section, formed by two opposed walls of greater width and two rounded walls of lesser width, characterized in that the procedure includes the following stages: a) commencing from a metal sheet (2), realisation of a plurality of corrugations (3) employing an embossing process; b) realisation of the bending of the metal sheet (2) employing a process of embossing or forming; and c) proceeding to weld the free edges (4) to close the tube (1), considering the tolerances required.
 2. A procedure according to claim 1, characterised in that, subsequent to stage c), cutting off the extreme ends (5) of the tube (1) is proceeded to.
 3. A procedure according to claim 1, characterised in that the corrugations (3) are embossed in those areas of the metal sheet (2) corresponding to the opposed walls of greater width of the tube (1) once fabricated, attaining part of the rounded walls of lesser width.
 4. A procedure according to claim 3, characterised in that the corrugations (3) are defined by a plurality of mutually parallel grooves transversely crossing said walls of greater width in a direction substantially diagonal to the axis of the tube (1).
 5. A procedure according to claim 1, characterised in that the corrugations (3) are embossed along the metal sheet (2) attaining extreme ends (5).
 6. A procedure according to claim 1, characterised in that the corrugations (3) are embossed along the metal sheet (2) avoiding extreme ends (5).
 7. A procedure according to claim 1, characterised in that the corrugations (3) are distributed in a manner being mutually non-equidistant, and non-symmetrical with respect to the bend line.
 8. A procedure according to claim 7, characterised in that the corrugations (3) are distributed maintaining the same angle of inclination such that once the metal sheet (2) has been bent, the corrugations (3) of one wall are positioned in a crossed manner with reference to those of the opposed wall, each pair of associated corrugations (3) defining a projection substantially in the form of an X.
 9. A procedure according to claim 1, characterised in that bending of the metal sheet (2) is realised along the middle in accordance with a longitudinal central line.
 10. A tube (1) for conveyance of a fluid of a heat exchanger of the type obtained employing the procedure for manufacture according to claim
 1. 11. A procedure according to claim 2, characterised in that the corrugations (3) are embossed in those areas of the metal sheet (2) corresponding to the opposed walls of greater width of the tube (1) once fabricated, attaining part of the rounded walls of lesser width.
 12. A procedure according to claim 11, characterised in that the corrugations (3) are defined by a plurality of mutually parallel grooves transversely crossing said walls of greater width in a direction substantially diagonal to the axis of the tube (1).
 13. A procedure according to claim 2, characterised in that the corrugations (3) are embossed along the metal sheet (2) attaining extreme ends (5).
 14. A procedure according to claim 3, characterised in that the corrugations (3) are embossed along the metal sheet (2) attaining extreme ends (5).
 15. A procedure according to claim 4, characterised in that the corrugations (3) are embossed along the metal sheet (2) attaining extreme ends (5).
 16. A procedure according to claim 2, characterised in that the corrugations (3) are embossed along the metal sheet (2) avoiding extreme ends (5).
 17. A procedure according to claim 3, characterised in that the corrugations (3) are embossed along the metal sheet (2) avoiding extreme ends (5).
 18. A procedure according to claim 4, characterised in that the corrugations (3) are embossed along the metal sheet (2) avoiding extreme ends (5). 